Correlation between canopy temperature based water stress indicators and soil water status in almond trees under simultaneous salinity and water stress

One of the non-invasive and remotely sensing method for measuring plant water status, and also irrigation automation, is using canopy temperature as an indicator. This study aimed to evaluate the combined effect of salinity and drought stress on almond water status. The trial was conducted based on randomized complete block design with three replications on a loamy sand soil. Treatments comprised three irrigation salinity levels viz. 2 (T1), 4 (T2), and 5 (T3) dSm-1. Canopy (Tc) and air (Ta) temperatures, relative humidity and integrated volumetric soil water content (SWC) at three depths (0˗20, 0˗40, and 0˗70) were measured at midday (12˗14) during the growing season. Results indicated that salinity has significant effect on Tc, Tc-Ta and available water depletion (AWD). Seasonal averages of Tc for treatment T1 to T3 were 31.9, 32.7 and 33.6 oC, respectively. Significant correlation was found between Tc, Tc-Ta, SWC and AWD. Threshold value of Tc for initiating stress in treatment T1 to T3 was obtained to be 31.6, 30.3 and 28.4 oC, respectively. Corresponding SWC for these Tc were 8.70, 11.01 and 14.07 %, respectively. High correlation between Tc and soil water status, shows that midday canopy temperature may be a useful tool for assessment of water status and precision irrigation scheduling of almond orchards.